Heating and cooling systems for houses and other dwellings and for at least some commercial establishments include a system for transmitting heated or cooled air throughout the dwelling or commercial establishment. These systems for transmitting heated or cooled air also include filtration equipment for removing particulate matter from the heated or cooled air and this filtration equipment, particularly for dwellings, normally includes one or more mechanical filters formed from fibrous materials.
These filter materials serve the function of mechanically blocking particulate matter that is in the air flowing in circuitous paths through the filter material. The particulate matter becomes attached to individual fibers and, over a period of time, progressively restricts the air flow paths. The difference in pressure between the inflow and outflow sides of the air filter increases as a function of the quantity and size of particulate matter trapped and retained by the filter. This trapped particulate matter simultaneously causes a reduction of the air flow rate through the filter.
This reduced air flow rate reduces the efficiency of the heating or cooling system and the effective heating or cooling of the dwelling or commercial establishment. The partially clogged filter also causes increased back pressure to be applied to the blower or fan which generates the air flow and this back pressure increases the work that must be performed and the energy consumed by the blower or fan unit. The resulting increased load increases the wear rate of the moving parts in the heating or cooling system and also results in increased operating costs. In view of these undesirable effects, it is important that partially clogged or dirty air filters be promptly replaced.
In order to determine when an air filter needs to be changed, a person normally must gain access to the filter. The filter must then be removed and visually inspected. If it is evident through this visual inspection that there is a significant build up of particulate matter on the outside surface of the air filter it is usually replaced with a new filter. This procedure has various deficiencies. This procedure means that the air filter must be periodically checked in order to determine when the filter needs to be changed. This is time consuming and can often result in dirty filters not being changed on time due to the failure to remember to check the filter. Also, the mere visual inspection of the air filter does not in many cases result in an accurate determination if the filter needs to be replaced. In this connection, one person may believe the filter is dirty but the next person may believe it is fine. The mere visual inspection of the surface of the filter is not that reliable in determining the condition of the filter because visual surface contamination or the lack of visual surface contamination may not be representative of contamination plugging microscopic flow paths inside the filter material.
In view of these problems, various devices have been developed over the years to determine when an air filter is dirty and needs replacement and to provide an indication of the need for replacement of an air filter in an heating and air conditioning system. Examples of such devices are set forth in U.S. Pat. Nos. 2,753,831 and 4,321,070 that describe a device with a tube which extends through an air filter and incorporates a whistle. In these devices, air flows continuously through a tube and as the air flow through the tube increases as a result of increasing clogging of the surrounding air filter, the whistle generates a sound when the air flow rate is of a sufficient magnitude. These devices have potential problems since contamination and clogging of the tube may occur and may have a negative effect upon the operation of the whistle. U.S. Pat. No. 2,804,839 discloses a device for providing a visual and audible signal indicative of the clogging of an air filter. The device uses a magnet for retaining a pivotable member in place that provides a visually perceivable indication and actuates further structure capable of energizing an audible alarm. All of these devices are difficult to install and require at least some support from the air filter itself which is undesirable since it can distort and damage the air filter.
These problems are overcome with the present air filter sensor apparatus kit that permits an air filter sensor to be easily installed to eliminate the need for actual inspection of the filter to determine when it is becoming clogged and needs to be replaced. This means that clogged or dirty air filters are more likely to be replaced on time. Moreover, the air filter sensor is supported by the air filter grill and not by the air filter and hence possible air filter damage is eliminated.